טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentKrokhmal Alexander
SubjectInvestigation of Gas Discharge Plasma Cathodes for
High-Power Electron Beam Generation
DepartmentDepartment of Physics
Supervisors Professor Emeritus Joshua Felsteiner
Professor Yakov Krasik


Abstract

The aim of the performed research is the investigation of plasma sources for the generation of electron beams with current density £102A/cm2 in vacuum diodes under an accelerating pulse £60kV/cm and pulse duration ≤10-6s. We investigated several gaseous hollow cathode (HC) and hollow anode (HA) plasma sources which differ from one another by their ignition schemes, namely arc and Penning sources and newly developed ferroelectric plasma sources (FPS). They can be used for the generation of electron beams with large cross-sectional area (>102cm2) and ignition and maintenance of high-current (1-2kA) low-pressure discharge.

It was shown that HC and HA high-current (≤2kA) gaseous discharge can be achieved at pressure of ~10-2-10-3Pa without the generation of explosive emission plasma at the electron source output grid. The discharge plasma electron density and temperature could be controlled by the amplitude of the discharge current in the range of 1011-1013cm-3 and 2-14eV, respectively. Without the accelerating pulse the plasma potential was £50V and it increased up to several kV during the accelerating pulse.

It was found that the FPS serves as a practically unlimited source of electrons due to the dense (~1014cm-3) surface plasma formation during the gaseous discharge. The use of the FPS allows one to design a compact high-current plasma electron source.

Several models were developed in order to explain the HC and HA operation. The obtained electron emission from the positively biased plasma is explained by the plasma ion dynamics in the vicinity of the HA output grid.